CurtPalme.com Home Theater Forum

stefuel · Posted: Tue Sep 22, 2009 11:20 pm Post subject: OK techsticles answer me this.

First, don't ask what I'm building. If I told you, I'd have to kill you Laughing

This is a general question of the description of operation of a multi-turn (or any) potentiometer. It's not that I don't understand the operation of what it does and how but rather how it's described in design. The wiper is a given. but for design purposes, which connection is considered + and -? Is there a standard for this or is it something decided by a flip of a coin during design? Rolling Eyes

jkruger · Joined: 24 Oct 2007 Posts: 2435 Location: Carlsbad, CA

Is it audio or linear? Audio pots have more resistance on one side than the other, and linear pots are the same on both sides.

Potentiometer tapers: http://sound.westhost.com/pots.htm#taper

**Curt Palme** · Posted: Wed Sep 23, 2009 12:08 am Post subject:

It also depends on how you're using the pot. (not the smoking kind!)

If it's a volume control, then looking at the front of the control with the leads facing down, the leftmost one is usually grounded, as that's when the volume is at 0, and the low level signal is shorted to ground. THe signal is usually fed into the rightmost one, and the center lead is the hot signal going to the power amp section. BUt... pots like the E'home filament voltage pot have no ground per se, you're only changing the resistance value in a circuit to vary the voltage going to the tubes. That pot in that application has no ground at all.

jkruger · Joined: 24 Oct 2007 Posts: 2435 Location: Carlsbad, CA

So there isn't really a + or - side. It's just a resistor.

jkruger · Joined: 24 Oct 2007 Posts: 2435 Location: Carlsbad, CA

And then there are these.. Digital Potentiometers:

http://www.analog.com/en/digital-to-analog-converters/digital-potentiometers/products/index.html

I never knew these existed until today.

**Curt Palme** · Posted: Wed Sep 23, 2009 2:57 am Post subject:

jkruger · Joined: 24 Oct 2007 Posts: 2435 Location: Carlsbad, CA

What? OH. Ya mean I shouldn't have bought those electrolytic potentiometers? I was hoping I could use them instead of variable differential capacitors. Wink

stefuel · Posted: Wed Sep 23, 2009 9:57 am Post subject:

These potentiometers are gear driven and provide positional feedback for large servo gear motors. The reason I'm asking is that I'm unsure of the results if they are wired wrong. I'd like to get it right the first time as the replacement servo motor pack is over $4K. My fear is that if the pot is telling the motor to turn clockwise to correct for position but it's really has to turn counter clockwise, it will lock up fighting it's self. I've got a 50/50 chance. Wanna bet I get it wrong the first time? Laughing

roland@b4 · Joined: 07 Jul 2009 Posts: 82 Location: Reading UK

Eventually you can make all pots multi-turn Smile

WTS · Joined: 08 Mar 2006 Posts: 1276 Location: Calgary

Pots aren't labeled with +/- they are labeled with CW/CCW/wiper

jkruger · Joined: 24 Oct 2007 Posts: 2435 Location: Carlsbad, CA

Is the controller smart enough to see the change in resistance going the wrong way in relationship to the output power?

stefuel · Posted: Wed Sep 23, 2009 10:09 pm Post subject:

jask · Joined: 17 Mar 2006 Posts: 10187 Location: kamloops BC

I ain't asking but from that description that sounds like the dream controller for my as yet to be built variable masking system... Wink

I would guess v=Voltage
g=Ground
s=sweeper
but I do not have to fix it if the magic smoke flies away, so good luck.